1. Field of the Invention
This invention is in the field of computer systems for monitoring and control. The present invention concerns an installation for monitoring and controlling a production machine or line for producing items or components which are subjected to production quality control with rejection of items or components which are not of a satisfactory standard, for precision measuring of the amounts of items produced and accepted as satisfactory, thereby to stop production when the required quantity of items has been produced.
2. Description of the Related Art
A problem which arises with some production machines or lines is that they may give rise to not inconsiderable levels or rejects products, which are often difficult to forecast by means of statistical calculations. This problem becomes more and more acute as the cost of production and in particular the cost of raw materials increases, thus requiring closer monitoring and control on the production process.
At the present time, use is made of counters for counting the number of items produced by the machine or line. However, as the proportion of items rejected as defective may vary relatively from one production process or machine to another, the total quantity of items produced as being satisfactory to the quality control procedure may often be greater than the actual quantity required. In fact, such an over-production is a necessary precaution or safety margin under present-day manufacturing conditions, so as to avoid any necessity to start up the installation again, to produce a small number of items, because the actual number of items produced in satisfactory form was in fact too low, because of the number of items rejected as defective. It will be appreciated in this connection that it is often very difficult or even impossible to achieve an accurate forecast of the number of items which will be found as defective and which will therefore have to be rejected, while in addition, as the costs involved in re-starting a production machine or line are substantial, production managers accept safety margins which may frequently turn out to be excessive, thus resulting in excessive quantities of items being produced, which in turn involves wastage of raw material, time and energy.
It has been noted that this kind of situation may occur in particular in printing processes, where it has been found that the losses due to an excessive print run, that is to say, an excessive number of items printed, particularly in the case of short printing runs, may be up to around 10%.
According to the present invention, there is provided an installation for monitoring and controlling a machine for producing items which at the end of production thereof are subjected to quality control with rejection of defective items, comprising a sensor for determining the number of items produced, a weighing means for supplying the weight of all the items rejected since the commencement of production, a precision weighing means for determining the mean weight of an item produced, a keyboard, display means, and a computing means connected to the sensor, weighing means, precision weighing means, keyboard and display means and operable on the basis of data supplied by the sensor, the weighing means and the precision weighing means to supply the display means with the number of items produced, the number of items rejected, and the number of acceptable items as constituted by the difference between the number of items produced and the number of items rejected.
The computing and operating program of the installation is introduced either from a disc or a magnetic tape, or the program may be contained in a read only memory of the unit which, by broad use of language, is referred to as the computing means.
As the production parameters are variable, when the machine is first set in operation, general re-initialisation is effected, by zeroing all the counters, followed by the introduction of the parameters relating to the production process to be carried out, such parameters corresponding to theoretical or reference values. In the course of the production process, as soon as possible, actual parameters will be determined by means of real measurement operations, and those parameters will be introduced into the installation, for example directly, by means of the precision weighing means or balance.
Although, as will be seen from the description hereinafter, a main purpose of the present monitoring and controlling installation is to stop operation of the production machine as soon as the reference or desired quantity of items has been produced, the installation also provide a large number of by-products or auxiliary data relating to the production procedure, the starting materials and the items produced.
In the course of production, the installation may also monitor the initial parameters and the parameters produced in the course of production, by measurements taken from point to point or from time to time to check for proper progress in regard to the mode of operation of the machine or to actuate an alarm signal, or even to stop the machine if certain programmed thresholds are exceeded.
Finally, the overall information produced may be utilised for invoicing, stock control, and the like.